Was the aim of the lecturer to teach law or to incite a random lynching? Or to make the co-students distrust each other for no more reason than they would want to distrust any other random person?

Go to a sufficiently large rock concert and the lead singer would be able to say “statistically at least one of you are a murderer!” Which might be “statistically correct” but all that would accomplish is for everyone to question his or her sanity.